Slip sheet for a planographic printing plate, production process thereof and a protected planographic printing plate and laminate thereof

Abstract

The present invention provides a slip sheet that protects a planographic printing plate in which the coefficient of static friction between corresponding surfaces of the slip sheet that contact an image-forming surface of the planographic printing plate is 0.35 or less, the surface strength of the slip sheet is 15 or more, or the Clark stiffness of the slip sheet is 20 to 50. In a production process of the planographic printing plate, the image-forming surface and the slip sheet are adhered by suitably charging, and following their lamination, the charge rapidly dissipates resulting in favorable separation, discharge characteristics and storage characteristics in an automatic plate feeder. In addition, sticking between the slip sheet and the image-forming surface during heat treatment can also be prevented simultaneously. This slip sheet is particularly effective for planographic printing plates of the heat mode type and photon mode type on which images are formed by exposure to laser light.

1. A slip sheet for a planographic printing plate that protects the planographic printing plate by having pulp fibers as a main constituent and a surface that contacts an image-forming surface of the planographic printing plate; and is physically separable from the planographic printing plate; wherein, the surface strength of the surface of the slip sheet is 15 or more and less than or equal to 26, a surface treatment agent containing a saponification product of an alkenyl dicarboxylic acid is coated onto the surface for preventing blocking between the image-forming surface and the slip sheet, and the surface resistance value of the surface of the slip sheet is 1.0×10 7  to 1.0×10 12  Ω. 
     
     
       2. A slip sheet for a planographic printing plate that protects the planographic printing plate by having pulp fibers as a main constituent and a surface that contacts an image-forming surface of the planographic printing plate; and is physically separable from the planographic printing plate; wherein, the Clark stiffness of the slip sheet is 20 to 50, the basis weight of the slip sheet is 40 to 60 g/m 2 , a surface treatment agent containing a saponification product of an alkenyl dicarboxylic acid is coated onto the surface for preventing blocking between the image-forming surface and the slip sheet, and the surface resistance value of the surface of the slip sheet is 1.0×10 7  to 1.0×10 12  Ω. 
     
     
       3. A slip sheet for a planographic printing plate according to  claim 2  that protects the planographic printing plate by having pulp fibers as a main constituent and a surface that contacts an image-forming surface of the planographic printing plate; and is physically separable from the planographic printing plate; wherein, the coefficient of static friction between the surfaces is 0.35 or less. 
     
     
       4. A slip sheet for a planographic printing plate according to  claim 1  or  2  wherein, the Beck's smoothness of the surface of the slip sheet that contacts the image forming surface of the planographic printing plate is 30 seconds or more. 
     
     
       5. A slip sheet for a planographic printing plate according to  claim 1  or  2  wherein, the Beck's smoothness of the surface of the slip sheet that contacts the image forming surface of the planographic printing plate is from 20 seconds to less than 60 seconds. 
     
     
       6. A slip sheet for a planographic printing plate according to  claim 2  wherein, the surface strength of the surface of the slip sheet is 15 or more. 
     
     
       7. A slip sheet for a planographic printing plate according to  claim 1  wherein, the Clark stiffness of the slip sheet is from 20 to 50. 
     
     
       8. A slip sheet for a planographic printing plate according to  claim 2  that protects the planographic printing plate by having pulp fibers as a main constituent; a top surface that contacts an image-forming surface of the planographic printing plate; and a back surface that does not contact the image-forming surface; and is physically separable from the planographic printing plate; wherein, the coefficient of static friction between the top surface and the back surface is 0.32 or less. 
     
     
       9. A slip sheet for a planographic printing plate according to  claim 2  that protects the planographic printing plate by having pulp fibers as a main constituent and a surface that contacts an image-forming surface of the planographic printing plate; and is physically separable from the planographic printing plate; wherein, the coefficient of dynamic friction between corresponding surfaces of the slip sheet is 0.32 or less. 
     
     
       10. A slip sheet for a planographic printing plate according to  claim 2  that protects the planographic printing plate by having pulp fibers as a main constituent and a surface that contacts an image-forming surface of the planographic printing plate; and is physically separable from the planographic printing plate; wherein, the coefficient of dynamic friction between the image-forming surface of the planographic printing plate and the surface of the slip sheet is 0.27 or less. 
     
     
       11. A slip sheet for a planographic printing plate according to  claim 1  or  2  wherein, the moisture content of the slip sheet is 1 to 10% by weight. 
     
     
       12. A slip sheet for a planographic printing plate according to  claim 1  or  2  that protects the planographic printing plate by having a surface that contacts an image-forming surface of the planographic printing plate and is separable from the planographic printing plate; wherein, a saponification product of an alkenyl dicarboxylic anhydride is added to a paper raw material for the slip sheet. 
     
     
       13. A protected planographic printing plate comprising a planographic printing plate, and a slip sheet according to  claim 1  or  2 , wherein:
 the planographic printing plate comprises an image-forming layer having an image-forming surface, and 
 the surface of the slip sheet contacts the image-forming surface of the image-forming layer. 
 
     
     
       14. A protected planographic printing plate according to  claim 13  wherein, the image-forming surface is a photosensitive surface for exposure to laser light. 
     
     
       15. A planographic printing plate according to  claim 14  wherein, the photosensitive layer for exposure to laser light is a positive photosensitive layer containing a photothermal conversion substance having an absorption range within the range of 600 to 1300 nm and an alkaline-soluble resin. 
     
     
       16. A laminate of a planographic printing plate composed by alternately laminating a slip sheet according to  claim 1  or  2  and a planographic printing plate. 
     
     
       17. A slip sheet for a planographic printing plate according to  claim 1  or  2 , wherein the surface treatment agent further comprises an acrylic polymer. 
     
     
       18. A slip sheet for a planographic printing plate according to  claim 12 , wherein an acrylic polymer is further added to the paper raw material. 
     
     
       19. A slip sheet for a planographic printing plate according to  claim 12 , wherein the surface treatment agent further comprises an acrylic polymer and an acrylic polymer is further added to the paper raw material. 
     
     
       20. A slip sheet for a planographic printing plate according to  claim 18  or  19  wherein, the acrylic polymer is a polymer or copolymer of an acrylic monomer selected from the group consisting of (meth)acrylic acid, (meth)acrylic esters, and (meth)acrylic amides. 
     
     
       21. The protected planographic printing plate according to  claim 13  wherein the photosensitive layer comprises an oxygen blocking layer. 
     
     
       22. A slip sheet for a planographic printing plate according to  claim 17  wherein, the acrylic polymer is a polymer or copolymer of an acrylic monomer selected from the group consisting of (meth)acrylic acid, (meth)acrylic esters, and (meth)acrylic amides.